Figure S6 Effects of warming (W), nitrogen addition (N) and their interactions on plant density, plant height and plant coverage of C3 plants and C4 plants from 2013 to 2022, based on a repeated-measures analysis of variance (ANOVA). Uppercase letters indicate significant difference in the plant density, plant height and plant coverage of C3 and C4 plants among treatments determined by Tukey’s HSD test at P <0.05.